In triangle ABC:
∠1 = 90°
According to the angle sum property:
∠1 + ∠2 + ∠3 = 180
Since angle 1 is 90 degrees
∠2 + ∠3 = 180 - 90
∠2 + ∠3 = 90° [∠1 + ∠2 + ∠3 = 180]
